There is known a vehicle power supply system which includes a high-voltage battery and high-voltage system equipment and in which the high-voltage battery and the high-voltage system equipment are cooled by a single cooling circuit (for example, refer to Patent Literature 1). Additionally, there is known a vehicle power supply system which includes a plurality of battery modules each having a plurality of high-voltage batteries and in which these battery modules are cooled by a single cooling circuit (for example, refer to Patent Literature 2).